Here is a screenshots from Apple's web site about the iPod Touch.
To sum it up, you do not need to use iTunes on a computer (PC or Mac) to buy and download music or apps.
The benefit of connecting it to a computer is to backup your music or apps in case of your iPod Touch gets replaced or, worst case, stolen. If either happens, you can connect your replacement iPod Touch, re-sync, and everything will be back to how you had it before.
--->Robert
8-)